Thermal and luminescence characterization of lanthanide 2,6-naphthalenedicarboxylates series

Abstract

The lanthanide 2,6-naphthalenedicarboxylates series of the formulas Ln 2(ndc) 3·nH 2O, where Ln = lanthanides from La(III) to Lu(III); ndc – C 10H 6(COO) 2 2−; n = 4, 4.5 or 5 have been prepared by the precipitation method. All obtained products were examined and characterized by elemental analysis, FTIR spectroscopy, simultaneous thermal analyses TG-DSC and TG-FTIR, X-Ray diffraction patterns as well as luminescence measurements. The crystalline compounds form three isostructural groups: Ce–Sm; La and Eu–Dy; Ho–Lu. In all complexes, the ndc 2− ligand appears in the deprotonated form. Heating of the complexes resulted in the multi-steps decomposition process. The dehydration process leads to the formation of stable crystalline Ln 2ndc 3 compounds which further decompose to the corresponding lanthanide oxides (air atmosphere). In argon atmosphere they decompose with releasing of water, carbon oxides and naphthalene molecules. The luminescence properties of Eu(III), Nd(III), Tb(III) and Er(III) complexes were investigated. The complexes of Eu(III) and Tb(III) emitted red and green light when excited by ultraviolet light whereas Nd(III) and Er(III) display emissions in the NIR region.